Synthesis of stilbene crown ether p-tert-butylcalix[4]arenes

Photo-switchable calixarene crown ether derivatives were synthesized in order to control the ring sizes and shapes of ionophores by isomerization between two different geometrical isomers. Five stilbene crown ether calix[4]arenes were prepared via McMurry coupling of the corresponding bisbenzaldehyde–calix[4]arene derivatives. The coupling reactions yielded both cis- and trans-stilbenes from o- and m-bisbenzaldehydes while only the cis-isomer was obtained from the reaction of the p-isomer. Unlike diazobenzene analogues, the stilbene crown ether calix[4]arene derivatives did not undergo thermal isomerization. Nevertheless, the isomerization of all synthesized stilbene crown ether calix[4]arenes can be photochemically induced.